There are many structural calculations to which aircraft parts and surfaces are submitted, and several measures and controls are applied to these parts and surfaces.
Among parts and surfaces of an aircraft which have been strictly measured and controlled we can mention primary moving surfaces, such as rudder, profounder and aileron. Such surfaces are specially submitted to measurement of the mass inertial moment, which is a geometrical magnitude of the solids measuring the movement resistance regarding its distributed mass. Thus, in case of primary moving surfaces, there is a need of assuring both control and accuracy of this measurement within acceptable tolerances in order to meet aeroelasticity requirements of those surfaces.
Equipment and methods enabling calculation or measurement of inertial moment of a solid body are known by the art, the document U.S. Pat. No. 5,309,753 being highlighted.
This document U.S. Pat. No. 5,309,753 describes an equipment and a method for determining the inertial matrix and the inertial product of a rigid body with irregular forms, such as a golf-club head. In that case, this equipment and method allow the experimental determination of mass center location and inertial moments of this type of solid bodies.
The equipment is formed by two “L” structures on which a cantilever bar is supported. The golf-club head is mounted in a cantilever bar in such a way that the golf-club cable axis is parallel with and below the cantilever bar. A cylindrical bar crosses perpendicularly the cantilever bar and a known weight is hanged in one of the ends of that cylindrical bar, preferably at the end opposed to the golf-club head. Then, the golf-club head moves towards x, y and z shafts, so as to get these coordinates for calculation of inertial moment. From those calculations and with the use of a pendulum movement of the solid body measured, products of inertia are calculated and an inertial matrix is built.
Although the equipment and method described in this document of the art allow to calculate the inertial moment of solid bodies and use the principle of compound pendulum, the equipment described herein tends to be limited for small solid bodies and would not support aircraft moving surfaces, such as rudder, elevator and aileron. The method to determine an inertial matrix of a rigid body in turn makes use of complex steps for determination of the inertial moment of the solid body used only as an intermediate stage to obtain products of inertia and inertial matrix